1. Field of the Invention
This invention relates to an ultrasonic bonding hone provided with a bonding pressing surface which extends in one direction and on which ultrasonic wave energy is concentrated, and to a method of ultrasonic welding using the ultrasonic bonding hone.
2. Description of the Related Art
In an automatic printing system which prints on a photographic paper by the use of a developed silver-salt photographic film, a roll of a photographic paper (will be simply referred to as “photographic paper roll”, hereinbelow) is used and the print is continuously made on the photographic paper roll while unrolling the photographic paper roll in the longitudinal direction. The photographic paper roll is prepared by rolling in a predetermined length a raw photographic paper split in a predetermined width and cutting it. When rolling the photographic paper roll, the trailing end portion of the raw photographic paper which is short of the predetermined length is bonded to the leading end portion of the raw photographic paper to be supplied next.
The photographic papers are bonded by ultrasonic welding. In this system, end portions of a pair of raw photographic papers to be bonded are overlaid one on the other, and a bonding pressing surface of an ultrasonic bonding hone on which ultrasonic wave energy is concentrated is pressed against the overlaid end portions to bond them. Further, there has been a system where an ultrasonic bonding hone with a knurled circumferential bonding pressing surface is used and the bonding pressing surface is pressed against the overlaid end portions while the ultrasonic bonding hone is being rotated. (See Japanese Unexamined Patent Publication No. 58(1983)-042049.)
The raw photographic paper comprises an emulsion layer, a resin layer, a cellulose (paper) layer and a resin layer laminated in this order, and resin layers of the pair of raw photographic papers are melt and flow together with the emulsion layers by the ultrasonic energy propagated through the bonding pressing surface in the ultrasonic welding. The fluidized body comprising the resin layers and the emulsion layers flows from the area where the pressing force is larger to the area where the pressing force is smaller, that is, according to high and low of the knurling and cured, whereby the overlaid photographic papers are bonded.
At this time, the emulsion layers are taken in by the molten resin and flow together with the molten resin. Though not flowing at this time, the cellulose layers deform in response to the pressing force by the bonding pressing surface and flowing of the fluidized body by the pressing force. For example, as shown in FIG. 9, there are formed in a pair of raw photographic papers T1 and T2, recesses Ha which are deformed by projections of the knurled surface and projections Hb which have not been deformed by projections of the knurled surface and correspond to recesses of the knurled surface.
In the ultrasonic welding, the fluidized body sometimes flows into an area on the raw photographic papers T1 and T2 outside the area R where the raw photographic papers T1 and T2 are pressed by the bonding pressing surface. The fluidized body flowing into such an area can be cured without being pressed to generate granular blocks S on the raw photographic papers T1 and T2 in the area outside the area R (FIG. 9). In this case, the blocks S are pinched between the photographic papers to leave pressing marks by the blocks S on the photographic papers when the raw photographic papers are rolled into a photographic paper roll, and the pressing marks deteriorate the quality of the photographic paper roll. That is, the quality of photographic paper roll sometimes deteriorates due to generation of the blocks S in the ultrasonic welding.